Technical Abstract:
The current high demand for quality protein and fiber production because of increasing world population has resulted in an intensification of agricultural production systems. As animal-based agriculture has evolved to larger production in subtropical regions of United States, the problems associated with manure handling, storage and disposal have grown significantly. This paper/review examines the following two key questions. (1) Are forage-based animal production systems as suggested by regulators a major source of non-point source nutrient pollution that contribute to the degradation of water quality in lakes, reservoirs, rivers, and ground water aquifers? and (2) Is properly managed cow-calf operations in subtropical agro-ecosystem would not likely be the major contributors to excess loads of nitrogen (N) or phosphorus (P) in surface water and/or groundwater? Understanding the effects of water-table management, nutrient dynamics and water quality in pastures is the key to reducing nutrients in runoff. All soils do not contribute equally to nutrient export from watersheds or have the same potential to transport nutrient to runoff nor would soil test levels accurately predict total dissolved nutrients. Better understanding of soil nutrient dynamics and other crop nutrient changes resulting from different management systems should allow us to predict potential impact on adjacent surface waters. These issues are critical and of increasing importance among environmentalists, ranchers, and public officials in many states. One of the first steps in assessing N or P level on any farm is to consider total N or total P inputs and outputs. In Florida, reduction of P transport to receiving water bodies is the primary focus of several studies because P has been found to be the limiting nutrient for eutrophication in many aquatic systems. Long-term monitoring of the changes in soil nutrients, especially soil P would enable us to predict soil chemical or physical deterioration that could occur under continuous forage-livestock cultivation and to adopt measures to correct them before they actually happen. Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal variability of nutrient dynamics across the entire landscape, especially in agricultural landscapes with cow-calf operations.